syscall failing

[mortenfc]

I added this to debug the syscall

auto fd = static_cast(syscall(__NR_perf_event_open, &pea, pid, cpu, mFd, flags));
std::cout << "errno after syscall: " << errno << std::endl;
if (-1 == fd) {
perror("Error occurred");
return false;
}

And I get

errno after syscall: 22
Error occurred: Invalid argument
errno after syscall: 2
Error occurred: No such file or directory

Why?

[mortenfc]

It turns out my vm did not have virtualized performance counters enabled, so only the SW events are working. I can't enable those performance counters for some CPU/bios reason. It would be good to print an error if HW performance counters can't be measured.